Process for increasing the hydrocracking activity of a supported nickel catalyst using phosphorous pentafluoride



United States Patent Office 3,144,414 Patented Aug. 11 1 964 3,144 414PROCESS FOR INCREASING THE HYDROCRACK- ING ACTIVITY OF A SUPPORTEDNICKEL CAT- AL YST UIN G PHOSPHOROUS PEN TAFLUORIDE Morris B. Srlverman,Portland, reg., assignor to Califorma Research Corporation, SanFrancisco, Calif., a corporation of Delaware No Drawing. Filed Mar. 21,1961, Ser. No. 97,167 1 Claim. (Cl. 252437) This invention relates to aprocess for increasing the hydrocracking activity of a supported nickelcatalyst in the presence of phosphorous pentafluoride.

As is well known to those skilled in the petroleum refining art,hydrocracking is a reaction wherein hydrocarbons are converted to lowerboiling products in the presence of added hydrogen and a catalyst atelevated temperature and pressure. It is also known that catalystshaving metallic nickel, or compounds thereof, disposed on active,siliceous supports promote hydrocracking, as, for example, theconversion of higher boiling petroleum distillates to lower boilinggasoline fractions. In general, it has been preferred to use a supportednickel sulfide catalyst rather than one containing metallic nickel,since the former promotes less hydrogenation, thereby producing aproduct containing more high octane number aromatic hydrocarbons andless saturated cyclic compounds.

I have found that the hydrocracking activity of a catalyst having nickelcomponent disposed upon an active, siliceous cracking support can beincreased by contacting the catalyst with phosphorous pentafluoride (PFDESCRIPTION OF CATALYST ACTIVATED BY THE PRESENT INVENTION The supportemployed in the catalyst, herein referred to as an active, siliceouscracking support, includes any natural or synthetic siliceouscomposition of acid character which is effective for the cracking ofhydrocarbons and which contains at least about 40 percent by Weight ofsilica, calculated as $0,, Illustrative of the cracking supports thatcan be employed are those natural cracking catalysts such as bentoniteand kaolin clays, and the conventional synthetic catalysts such assilica-alumina, silicamagnesia, silica-zirconia, andsilica-alumina-zirconia. In addition, satisfactory supports are thesynthetic metal aluminum silicates (such as the synthetic chabazites,commonly referred to as molecular sieves) that impart the necessarycracking activity to the catalyst. A preferred active, siliceouscomponent comprises synthetically prepared composites of silica andalumina containing from 70 to99 percent of the silica component.

The above-noted siliceous cracking catalysts, which form the support ofthe present catalyst, can be prepared by any known method. For example,synthetic silicaalumina composites can be prepared by combining anaqueous solution of an aluminum salt, suitably adjusted in acidity witha solution of sodium silicate under such conditions that thecorresponding gels are coprecipitated in intimate admixture. Or, silicagel and alumina gel can be separately prepared and then mixed in thedesired proportions. Alternatively, a formed. silica gel can be treatedwith an aqueous solution of an aluminum salt, and the aluminaprecipitated in the silica gel by the addition of a precipitant. Inanother method, the silicaalumina can be prepared by first forming anacidstabilized silica sol and then adding an adsorptive alumina to raisethe pH and cause the gelation of the mixture. If desired, varioushalides can be incorporated in the support to give additional acidity.

After preparation of the siliceous cracking component, the latter ispreferably impregnated with an aqueous solution of a water-soluble saltof nickel. The concentration of the salt in this solution and thequantity of solution used to impregnate the support is such that from 1to 35 percent, and preferably 2 to 25 percent, of nickel is disposed onthe cracking support. Representative salts which may be employed toeffect said impregnation are the chlorides, nitrates and acetates ofnickel, although other decomposable salts may be employed if desired,including various metallo-organic compositions such as the chelates.Instead of following the foregoing impregnation procedure, the nickelsalts can be incorporated in the siliceous catalyst component as thesame is being formed.

Following compositing of the nickel with the siliceous support, thecatalyst can be dried at a temperature of from about 200 to 500 F. andthen calcined at a temperature of from about 800 to 1200 F. for an houror more. Preferably, the impregnated support is subjected to aheat-treating (thermactivation) step, whereby it is heated to atemperature in the range of from about 1200" to 1600 F., and preferablyin the range of from about 1300" to 1550 F. This heat-treating step canbe conducted in several ways. The preferred method is to contact theparticulate, substantially oxidized nickel impregnated support with arelatively dry (having a water vapor partial pressure of less than about0.5 p.s.i.a.), nonreducing gas such as air, nitrogen or carbon dioxideat a rate which is preferably at least 10 cubic feet per hour per cubicfoot of catalyst (10 VHSV) at a temperature Within the noted range andat a pressure which can be atmospheric, or superatmospheric.Additionally, thermactiva'tion can be done by contacting the catalystmass at a temperature of from l200 to 1600 F. under a pressure of lessthan about 1 millimeter of mercury absolute. In either method, thecontact time should extend over a period of from about 0.25 to 48 hours.When lower temperatures of the l200 to 1600 F. range are employed, say,from 1200 to 1350 F., contact periods over 24 hours are particularlyeffective; whereas at the higher temperatures of 1500 and 1600 F.,periods of from 15 to minutes are more appropriate.

Following drying and calcining, or thermactivation if such is employed,the nickel oxide component on the catalyst can be reduced, if desired,by contacting the catalyst with hydrogen at atmospheric pressure whileheating from room temperature to about 600 to 900 F. at a rate of about100 F. per hour, and thereafter contacting the catalyst with hydrogen atelevated pressures (1500 p.s.i.g., for example) and temperature (550 to900 F.) for an hour. Preferably, the nickel component of the catalyst isconverted, at least partially, to the sulfide by contacting the nickeloxide or, preferably, metallic nickel, with hydrogen sulfide or withhydrogen and a low molecular weight mercaptan or organic sulfide, orwith hydrogen and a hydrocarbon containing a dissolved sulfur compound,at temperature below about 750 F.

The catalyst can be used in the form of pellets, beads, extruded orother particle shapes. Good results have been obtained with a catalystmass made up of small beads (average diameter of A; inch) as well aswith a crushed aggregate prepared from such beads. The catalyst can alsobe ground to a fineness suitable for fluidized operations.

ACTIVATION METHOD can also be done by phosphorous pentafiuoride gasalone or in admixture with other gases such as hydrogen, hydrocarbons,and the like. The contact should be such that at least 0.5 weightpercent of the catalyst is PF Preferably, the amount should exceed about1.0 weight percent. It has been found that PF percentages above about5.0 weight percent do not increase the hydrocracking activityappreciably. The activation can be done on freshly prepared catalyst orfollowing catalyst regeneration, the latter being conducted byconventional oxidation techniques.

The catalyst can also be activated by dissolving PR; in a hydrocarbonliquid, such as feed, hexane, etc., that does not react with the PF andthen contacting the catalyst, either before the catalyst is employed inthe reaction zone or actually during its use in the reactor.

UTILITY OF ACTIVATED CATALYST As noted, the activated catalyst of thepresent invention is particularly suitable for use in hydrocracking suchpetroleum distillates as naphthas, kerosenes, gas oils, cycle oils andthe like. These distillates can be of straight run origin or derivedfrom the efiluents of various petroleum processing operations, such asthermal or catalytic cracking, reforming, hydrofining and otherWellknown refining processes. Also, feeds derived from such sources asshale, gilsonite, coal tar distillates are suitable. Generally, thesefeeds boil in the range of from about 200 to 900 F. or more. Further,the feeds are preferably free of compounds that are known to adverselyaffect catalytic activity, such as those containing oxygen and/ornitrogen.

The feedstock can be introduced to the hydrocracking zone as either aliquid, vapor, or mixed liquid-vapor phase, depending upon thetemperature, pressure, proportions of hydrogen and boiling range of thecharge stock utilized. The feed is generally introduced in admixturewith at least 750 s.c.f. (standard cubic feet) of hydrogen per barrel oftotal feed (including both fresh as well as recycle feed, if the latteris employed). With feedstock such as naphthas, gas oils and cycle oils,at least 500 s.c.f. of hydrogen are normally consumed in thehydrocracking zone per barrel of total feed converted to syntheticproducts, i.e., those lower molecular weight products boiling below theinitial boiling point of the fresh feed. The hydrogen stream admixedwith the incoming feed can be conveniently made up of recycle gasrecovered from the etliuent from the hydrocracking zone, together withfresh make-up hydrogen.

The hydrocracking conditions employed in the hydrocracking zone can bevaried over relatively wide ranges of temperature, pressure and feedspace velocity, but certain more narrowly-defined portions of theseranges are preferred.

In general, the hydrocracking reaction may be conducted at temperaturesranging from about 350 to 800 F. or even higher, but it is preferredthat they be maintained within the range of from about 400 to 700 F. asit has been found that the product distribution is much more favorablewhen the reaction is conducted within the noted low temperaturepreferred range. The pressures employed in the hydrocracking zone are inexcess of about 150 p.s.i.g. and may range upwardly to 2500 or 3000p.s.i.g., with a preferred range being a total pressure of from about500 to 2000 p.s.i.g. when employing naphthas, gas oils and cycle oils asfeedstocks. Somewhat lower pressures can be employed when singlemolecular species-type feedstocks are employed. Generally, thehydrocracking zone feed may be introduced into the reaction zone at aliquid hourly space velocity (LHSV) of from about 0.1 to 20.0 or morevolumes of hydrocarbon (calculated as liquid) per superficial volume ofcatalyst per hour (v./v./hr.) with a preferred rate being from about 0.5to 15.0 v./v./hr.

TEST PROCEDURE As hereinbefore noted, the catalyst activation method ofthe present invention produces a hydrocarbon conversion catalyst ofenhanced activity. Inasmuch as the subject catalyst has particularutility in hydrocracking reactions, this enhanced activity can best beshown by a test employing such a reaction. In this test, the so-calledactivity index of each catalyst can be determined and compared. Thehigher the activity index, the more active the catalyst is forhydrocracking, since it refers to the degree of conversion to syntheticproducts.

This test to determine the activity index of the catalyst broadlyinvolves a determination of the conversion of a standard and readilyobtainable hydrocarbon feedstock of efined physical and chemicalcharacteristics to products falling below the boiling point of saidstock under defined operating conditions. The feedstock employed is acatalytic cycle oil recovered as a distillate fraction from the effiuentof a fluid-type catalytic cracking unit, the recovered fraction beingone containing essentially equal proportions of aromatics and ofparaffins plus naphthemes, and boiling over a range of fromapproximately 400 to 575 F., as determined by ASTM D-158, prior to anyhydrofining treatment given the feed to reduce its basic nitrogencontent at a level below 5 p.p.m., this being the maximum amountpermitted in the test feed. The specific test feed employed in obtainingthe activity index values of all catalysts given herein was obtainedfrom a fluid catalytic cracking unit being charged with a mixture oflight and heavy gas oils cut from a Los Angeles Basin crude. This cycleoil test feed had a gravity of 28 API, an ASTM D-158 start of about 400F. and a basic nitrogen content of about 175 p.p.m. The test stock washydrofined by passing the same, along with 3500 s.c.f. of hydrogen perbarrel of naphtha through a hydrofining catalyst containing cobalt oxide(2 percent cobalt) on a coprecipitated molybdena-alumina (9 percentmolybdenum) support at a pressure of 800 p.s.i.g., and LHSV of 1, and ata temperature between 700 and 750 F. This hydrofining operation wasaccompanied by a hydrogen consumption of 300 to 400 s.c.f. of hydrogenper barrel of feed and resulted in a reduction of the basic nitrogencontent in the liquid efiluent to less than 5 p.p.m. The hydrofined teststock had the following inspections.

Table I.Inspecti0ns of Hydrofined Cycle Oil T est Sample Gravity, API 30Aniline point, F 93 Nitrogen (basic), p.p.m Below 5 Aromatics, vol.percent 48 Olefins, vol. percent 1 Parafiins-l-naphthenes, vol. percent51 ASTM Distillation (D-158), F.:

Start 357 532 End point 570 The equipment employed in determining theactivity index of the catalyst is a conventional continuous feed pilotunit, operated once-through with hydrocarbon feed and hydrogen gas. Itconsists of a cylindrical reaction chamber operated downflow with apreheating section, followed by a section containing the catalyst undertest, and enclosed in a temperature controlled metal block to permitcontrolled temperature operation, together with the necessaryappurtenances, such as feed burettes, feed pump, hydrogen supply,condenser, high-pressure separator provided with means for sampling thegas and liquid phases, back pressure regulators, and thermocouples. Foraccuracy in hydrogen feed, hydrogen is compressed into a hydrogenaccumulator or burette whence it is fed to the reactor by displacementwith oil fed at constant rate from a reservoir by means of a pump.

In testing a catalyst to determine its activity index, the foregoinghydrofined cycle oil test stock, along with 12,000 s.c.f. of hydrogenper barrel of feed, is passed through a mass of catalyst (50 ml. wereactually employed) at a liquid hourly space velocity of 2 and at afurnace temperature of 570 F. The run is continued for 14 hours underthese conditions, with samples being collected at about two-hourintervals. These samples are allowed to flash off light hydrocarbons atambient temperature and pressure, following which a determination ismade of the API gravity of each sample. The aniline point of the samplesmay also be determined when it is desired to obtain an indication of therelative tendency of the particular catalyst to hydrogenate aromaticspresent in the feed. The individual API gravity values are then plottedand a smooth curve is drawn from which an average value may be obtained.Samples collected at the end of the eighth hour of operation are usuallyregarded as representative of steady-stage operating conditions and maybe distilled to determine conversion to products boiling below theinitial boiling point of the feed. This conversion under steady testconditions is a true measure of the activity of the catalyst. However,the API gravity rise, that is, the API gravity of the product sample orsamples minus the API gravity of the feed, is a rapid and convenientmethod of characterizing the catalyst which correlates smoothly withconversion. For convenience, the foregoing API gravity rise is referredto as the activity index of the catalyst.

While reference has been made above to the use of a particular catalyticcycle stock in connection with determining the activity index of thecatalyst, it is believed that similar activity index values can beobtained with catalytic cycle stocks obtained from other than Californiacrudes provided the sample employed as feed has substantially the samecharacteristics as that of the feed described above. While the use ofsuch other test feeds may give slightly different absolute values thanthose described herein, such differences are without influence onconclusions reached relating to catalyst activity inasmuch as the teststock is serving primarily as a relative standard by which to judge theconversion activity of the catalyst.

EXAMPLE 1 Five separate catalyst samples were prepared by im pregnatingsilica-alumina (90 percent to percent by weight, respectively) crackingcatalyst with about 2.5 weight percent nickel. Following impregnation,the catalysts were dried, calcined at about 1000 F. and thermactivatedat about 1400 F. for 24 hours in a stream of air. The catalysts werethen sulfided by contact with methyl disulfide and hydrogen at 570 F.One of the samples was set aside and designated Catalyst A.

Phosphorous pentafluoride gas was prepared by heating CaF with P 0 in a10:1 (respectively) molar ratio. Gaseous PF was then added (at about 450F.) to the four remaining catalyst samples such that the Weight percentPF on the samples varied from 1.0 to 3.9 (based on the weight of theentire catalyst). These four catalysts were designated Catalysts B, C, Dand E.

The five catalysts were then subjected to the 570 F. activity testdescribed above. The activity indices after eight hours on-stream foreach catalyst are shown in Table II.

Table 11 Wt. per- Catalyst cent P11 Activity on Oata- Index lyst Fromthe above table, it can be seen that the PF activated catalysts wereconsiderably more active for hydrocracking than non-activated CatalystA, particularly at the higher PF percentages.

It might be noted that the same catalyst as Catalyst A which Wascontacted with enough 5 M phosphoric acid to form nickel phosphate fromabout 88 percent of the nickel on the support was not enhanced withrespect to hydrocracking activity, but, to the contrary, was actuallyreduced to an activity less than the original catalyst.

EXAMPLE 2 A catalyst prepared in the same manner as described in Example1, except that it was only calcined and not thermactivated (activityindex less than 12), was contacted with PF such that the final catalysthad 4.0 weight percent (of the total catalyst) PF disposed thereon. Theactivated catalyst had a 570 F. activity index of 22.3. The enhancedeffect of the PE; activation on this catalyst is readily apparent.

I claim:

A process for increasing the hydrocracking activity of a catalystconsisting essentially of from 1 to 35 weight percent (as the metal) ofnickel sulfide disposed on an active siliceous cracking support, saidsupport containing at least 40 weight percent silica, which comprisescontacting said catalyst with a phosphorous pentafiuoridecontainingfluid at a temperature in the range of from about to 1000 F. for aperiod sufiicient such that at least 0.05 weight percent of the finalcatalyst is PF References Cited in the file of this patent UNITED STATESPATENTS

